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Estimate for a house in SF with a typical roof and typical electric bill. $20k upfront cost. $4k in savings over 20 years. That's an implied rate of return o

Estimate for a house in SF with a typical roof and typical electric bill. $20k upfront cost. $4k in savings over 20 years. That's an implied rate of return of 0.9% annually. No thanks.

stainablesteel 2y ago
i've heard of some business models that install these and have you pay what would be the difference to your electric bill to the company until they pay themselves off, not sure if the panels last long enough to make that work though
- ccozan 2y ago
  Yes. In Germany they are selling a lot of models, but none, I mean, really, none asked about the rentability. So I went to a neighbour who just installed his 25kW and was very proud and happy, and asked him, in how many years is the return of investment. Siderated, he could not answer and then a few days later, with a very stern face: 25 years or more because if more people install these, the price that the city is paying for the pumped energy goes down. So no. 20kw is not the answer. I showed my setup: 3.5kw + big battery. Pays the bill approx 60 70% of the daily usage. Investment payback : 5years.
  - BonoboIO 2y ago
    Damn, your neighbor got robbed by the installer …
  - scotty79 2y ago
    What if he added previous generation crypto miner (so it's cheap) and use the excess electricity instead of selling it to the grid? This could also save some money on heating in winter unless he has a heat pump priced in already.
    - PaulDavisThe1st 2y ago
      prev gen crypto mining is phenomenally inefficient in terms of energy that ends up being converted to heat, but it is absolutely not what you would use to take electricity and create heat given any other choices.
      - scotty79 2y ago
        What are other choices? Heat pump is obviously the best but any other thing is just electric heater with 100% efficiently of heat generation. Pushing some bits around doesn't change that. I guess for some applications you might prefer higher temperatures but for residential heating crypto mining is as good as anything else, right?
    - ccozan 2y ago
      this guy is a carpenter :). cryto mining would sound like chinese to him...
  - throwaway2037 2y ago
    25kW? That is crazy huge! How many panels? What does this guys house (mansion!?) look like? Google tells me that average installation size is about 7-8kW.
    - ccozan 2y ago
      Is not that big. you have approx 400W ( mine are 440W) on a 2sqm. Hi sroof is like 15 x 8 m. and is not fully covered. You can easily reach 25kw.
- buckle8017 2y ago
  Yes I think in general those are a better deal for the homeowner. They're a terrible deal for those companies investors though. Presumably at some point they go bankrupt and sell your roof at auction??? weird setup
- dzhiurgis 2y ago
  One of these wouldn't sign me up as they couldn't offer any savings (92% of my use is off peak, around 16ct NZD (9 USD) / kWh). A lot of the time such companies pray on people on stupid plans (or those paying thru the nose for "exclusively renewable") power.
  - nine_k 2y ago
    This exactly the case when a battery would make an immense difference. (9 USD / kWh sounds terrifying. Not only an electric kettle begins to cost you; probably playing computer games at high quality / resolution comes with a noticeable price tag in electricity that the GPU would eat.)
    - bruce511 2y ago
      I think he meant 9 USD cents per kw. (He included ct with NZD but forgot it with USD.)
  - throwaway2037 2y ago
    Woah, your electricity is so cheap! Is it mostly hydro?
prdonahue 2y ago
Was that paired with a battery? Under NEM3 (and reduced net metering rate), it doesn't make sense to install PV in California without a battery.
ggreer 2y ago
How are you calculating that? Solar installations are around $2.50-$3.50 per watt, so $20k would get you 6-8kW. Assuming actual output is 10% of capacity, that's 14-19kWh/day or 5,000-7,000kWh per year. Current residential electricity prices in SF are 38.9 cents per kWh[1], so that's $2,000-2,700 per year in savings, or $40-54k over 20 years. The actual amount saved depends on how much electricity you're consuming during peak times, but I doubt that number is off by a factor of 10. 1. https://www.bls.gov/regions/west/news-release/averageenergyprices_sanfrancisco.htm https://www.bls.gov/regions/west/news-release/averageenergyp...
- buckle8017 2y ago
  I didn't calculate anything I just put in an address and a monthly electricity bill. https://sunroof.withgoogle.com/ https://sunroof.withgoogle.com/
  - Retric 2y ago
    Ahh, ok the tool sucks it doesn’t seem to calculate based on your current cost per kWh or the local cost per kWh. It’s ignoring inflation on those calculations, acting like your electric bill will be the same in 20 years. It’s also ignoring residual value in the system after 20 years they typically last 25-30, and you don’t pay taxes on savings. There install estimates where also really high for my area, but I don’t know if that’s a general issue.
    - patrickhogan1 2y ago
      Your electric bill 20 years from now is just as likely to go down as it is to go up. In two decades, we could see advancements like mobile generators offering free power, ultra-affordable battery packs delivered to homes to meet energy needs, or even the widespread adoption of low-cost fusion energy. The key takeaway is that predicting the future cost of electricity is as challenging as it was to predict today’s solar energy costs—now far lower than anyone expected.
      - 2y ago
malfist 2y ago
Solar installations have a 30% tax rebate currently. So your $20k would actually be $12k, makes the math a bit better. Plus, are you counting in inflation of electricity prices in those 20 years? I'm sure electricity isn't going to get cheaper
deleted 2y ago
[deleted]
bokohut 2y ago
I find this argument short sighted time and again based on personal life experiences as a former electrician given the life impacting results I have witnessed from power losses. My electrical experiences are regional to my area in the NorthEast US where long duration events have caused many thousands of US dollars in lost food, tens of thousands of dollars in losses from flooded basements, and when temperatures in Winter often drop below freezing and the power goes out pipes begin to freeze causing even more damage structure wide. In time we will see insurance companies reducing rates for those with local energy storage as the corporate insurance machine catches up to understand the benefits of having such power storage locally. I laugh when people make this exact financial reasoning argument because so few people look at the big picture and fail to comprehend the impacts to their life when that switch on the wall leaves one in the dark. Then again I have designed and architected many successful software systems for high availability and my foundational starting point with any system is always energy. Most of those in society assume that switch will always turn on that light and when it does not then those impacted begin to realize what a "centralized grid" truly means. Decentralizing the grid is already happening as CA very recently announced any new residences built as of 2026 and beyond must be constructed with PV and storage. Individuals can act in ignorance on the energy problems for now however in time everyone will be forced to participate as the issues continue to compound. Proactive versus reactive, because by the time it matters it will already be too late.
- therealdrag0 2y ago
  My plan is just to use my EV with generator interconnect to house with V2L. No color or gas needed. Ioniq can run house for like 5 days.

Estimate for a house in SF with a typical roof and typical electric bill. $20k upfront cost. $4k in savings over 20 years. That's an implied rate of return of 0.9% annually. No thanks.

stainablesteel 2y ago

i've heard of some business models that install these and have you pay what would be the difference to your electric bill to the company until they pay themselves off, not sure if the panels last long enough to make that work though

ccozan 2y ago
Yes. In Germany they are selling a lot of models, but none, I mean, really, none asked about the rentability. So I went to a neighbour who just installed his 25kW and was very proud and happy, and asked him, in how many years is the return of investment. Siderated, he could not answer and then a few days later, with a very stern face: 25 years or more because if more people install these, the price that the city is paying for the pumped energy goes down. So no. 20kw is not the answer. I showed my setup: 3.5kw + big battery. Pays the bill approx 60 70% of the daily usage. Investment payback : 5years.
- BonoboIO 2y ago
  Damn, your neighbor got robbed by the installer …
- scotty79 2y ago
  What if he added previous generation crypto miner (so it's cheap) and use the excess electricity instead of selling it to the grid? This could also save some money on heating in winter unless he has a heat pump priced in already.
  - PaulDavisThe1st 2y ago
    prev gen crypto mining is phenomenally inefficient in terms of energy that ends up being converted to heat, but it is absolutely not what you would use to take electricity and create heat given any other choices.
    - scotty79 2y ago
      What are other choices? Heat pump is obviously the best but any other thing is just electric heater with 100% efficiently of heat generation. Pushing some bits around doesn't change that. I guess for some applications you might prefer higher temperatures but for residential heating crypto mining is as good as anything else, right?
  - ccozan 2y ago
    this guy is a carpenter :). cryto mining would sound like chinese to him...
- throwaway2037 2y ago
  25kW? That is crazy huge! How many panels? What does this guys house (mansion!?) look like? Google tells me that average installation size is about 7-8kW.
  - ccozan 2y ago
    Is not that big. you have approx 400W ( mine are 440W) on a 2sqm. Hi sroof is like 15 x 8 m. and is not fully covered. You can easily reach 25kw.
buckle8017 2y ago
Yes I think in general those are a better deal for the homeowner. They're a terrible deal for those companies investors though. Presumably at some point they go bankrupt and sell your roof at auction??? weird setup
dzhiurgis 2y ago
One of these wouldn't sign me up as they couldn't offer any savings (92% of my use is off peak, around 16ct NZD (9 USD) / kWh). A lot of the time such companies pray on people on stupid plans (or those paying thru the nose for "exclusively renewable") power.
- nine_k 2y ago
  This exactly the case when a battery would make an immense difference. (9 USD / kWh sounds terrifying. Not only an electric kettle begins to cost you; probably playing computer games at high quality / resolution comes with a noticeable price tag in electricity that the GPU would eat.)
  - bruce511 2y ago
    I think he meant 9 USD cents per kw. (He included ct with NZD but forgot it with USD.)
- throwaway2037 2y ago
  Woah, your electricity is so cheap! Is it mostly hydro?

prdonahue 2y ago

Was that paired with a battery? Under NEM3 (and reduced net metering rate), it doesn't make sense to install PV in California without a battery.

ggreer 2y ago

How are you calculating that? Solar installations are around $2.50-$3.50 per watt, so $20k would get you 6-8kW. Assuming actual output is 10% of capacity, that's 14-19kWh/day or 5,000-7,000kWh per year. Current residential electricity prices in SF are 38.9 cents per kWh[1], so that's $2,000-2,700 per year in savings, or $40-54k over 20 years. The actual amount saved depends on how much electricity you're consuming during peak times, but I doubt that number is off by a factor of 10. 1. https://www.bls.gov/regions/west/news-release/averageenergyprices_sanfrancisco.htm https://www.bls.gov/regions/west/news-release/averageenergyp...

buckle8017 2y ago
I didn't calculate anything I just put in an address and a monthly electricity bill. https://sunroof.withgoogle.com/ https://sunroof.withgoogle.com/
- Retric 2y ago
  Ahh, ok the tool sucks it doesn’t seem to calculate based on your current cost per kWh or the local cost per kWh. It’s ignoring inflation on those calculations, acting like your electric bill will be the same in 20 years. It’s also ignoring residual value in the system after 20 years they typically last 25-30, and you don’t pay taxes on savings. There install estimates where also really high for my area, but I don’t know if that’s a general issue.
  - patrickhogan1 2y ago
    Your electric bill 20 years from now is just as likely to go down as it is to go up. In two decades, we could see advancements like mobile generators offering free power, ultra-affordable battery packs delivered to homes to meet energy needs, or even the widespread adoption of low-cost fusion energy. The key takeaway is that predicting the future cost of electricity is as challenging as it was to predict today’s solar energy costs—now far lower than anyone expected.
    - 2y ago

malfist 2y ago

Solar installations have a 30% tax rebate currently. So your $20k would actually be $12k, makes the math a bit better. Plus, are you counting in inflation of electricity prices in those 20 years? I'm sure electricity isn't going to get cheaper

deleted 2y ago

[deleted]

bokohut 2y ago

I find this argument short sighted time and again based on personal life experiences as a former electrician given the life impacting results I have witnessed from power losses. My electrical experiences are regional to my area in the NorthEast US where long duration events have caused many thousands of US dollars in lost food, tens of thousands of dollars in losses from flooded basements, and when temperatures in Winter often drop below freezing and the power goes out pipes begin to freeze causing even more damage structure wide. In time we will see insurance companies reducing rates for those with local energy storage as the corporate insurance machine catches up to understand the benefits of having such power storage locally. I laugh when people make this exact financial reasoning argument because so few people look at the big picture and fail to comprehend the impacts to their life when that switch on the wall leaves one in the dark. Then again I have designed and architected many successful software systems for high availability and my foundational starting point with any system is always energy. Most of those in society assume that switch will always turn on that light and when it does not then those impacted begin to realize what a "centralized grid" truly means. Decentralizing the grid is already happening as CA very recently announced any new residences built as of 2026 and beyond must be constructed with PV and storage. Individuals can act in ignorance on the energy problems for now however in time everyone will be forced to participate as the issues continue to compound. Proactive versus reactive, because by the time it matters it will already be too late.

therealdrag0 2y ago
My plan is just to use my EV with generator interconnect to house with V2L. No color or gas needed. Ioniq can run house for like 5 days.